1. Field of the Invention
This invention relates to guide rolls, and, more particularly, to a guide roll construction suitable for conveying hot works, for example, in continuous metal casting operations, ingot-making operations or in an anterior stage of hot rolling in the steel-making or similar industry.
2. Description of the Prior Art
Conventional guide rolls of this sort are generally constituted by a steel roll shaft of unitary construction to secure necessary strength and are internally provided with a cooling water passage for enhancing the heat resistance of the roll shaft. In some cases, for the purpose of increasing the thermal resistance, there have been used guide rolls with a heat resistance metal surfacing or guide rolls of a composite construction having a sleeve or rings of heat resistant material integrally fitted on the circumference of the roll shaft. However, the conventional integral type guide rolls are unsatisfactory with respect to heat resistance, resistance to thermal shock, resistance to abrasive wear and mechanical strength which are essential for the guide rolls to be used for guiding workpieces of high temperature, in the absence of a unitary or composite material which can meet all of these requirements. With guide rolls of integral construction, maximum stress occurs in the center portion of the circumference of each roll shaft due to the bending caused by the reaction force imposed on the high temperature workpiece during its transfer, and it is extremely difficult to cope with it in terms of the high temperature strength of the roll material.
Further, in the continuous casting process, there is an increasing trend toward energy conservation, retaining the heat of the hot cast stock while it is transferred after severing and utilizing its heat effectively in the subsequent hot rolling. In the continuous casting operation, the guide rolls which convey a continuously cast strip from a water-cooled mould to a shearing machine are subjected to a high temperature above 1000.degree. C. so that more severe conditions are imposed on such guide rolls. In order to lessen thermal deterioration in strength, which will shorten the service life of the guide rolls, and to reduce the heat dissipation from the workpiece to the rolls, it has been proposed to use ceramic material which has high heat resistance along with a high heat insulating property, e.g., embedding a ceramic material in axial or circumferential grooves provided on the circumference of a roll shaft or a sleeve of a heat resistant material which is integrally fitted on a water-cooled roll shaft as mentioned hereinbefore, or mounting a plurality of ceramic pieces on the circumference of a heat insulating sleeve by the use of a corresponding number of fixing means. The conventional guide rolls of this sort are invariably complicated in construction and therefore require an increased number of steps in the machining stage of the roll shaft or the heat insulating sleeve to be fitted on the roll shaft, coupled with the problem that the service life of the fixing means is shortened considerably by thermal fatigue as a result of subjection to the heat of the high temperature workpiece. In addition, the roll as a whole has to be replaced in the event of a damage occurring to a certain part of the roll since a long time period is required for repair.